Prior art filling machines comprise a rotary carousel equipped with a plurality of peripheral holders for supporting the individual containers to be filled.
Each holder is provided with a dispensing device designed to fill the respective container with a certain amount of product from a containment tank.
Prior art dispensing devices consist of a hollow housing extending along a vertical axis, a shutter mounted inside the housing and an actuating unit adapted to move the shutter within the housing.
The hollow housing of the dispenser partly defines a dispensing conduit. The dispensing conduit has an inlet opening and an outlet opening for the product. From the containment tank the product flows through the inlet opening into the dispensing conduit and from there through the outlet opening into the containers to be filled.
The shutter allows the outlet opening of the dispensing conduit to be opened and closed. More specifically, by moving the shutter axially, the actuating unit controls the opening and closing of the outlet opening.
The shutter actuating unit is sealed off from the dispensing conduit by a flexible membrane. More specifically, the membrane connects the shutter with the hollow housing of the dispenser because the shutter itself goes through the membrane.
The membrane guarantees art aseptic environment inside the dispensing conduit by preventing the product to be filled into the containers from being contaminated by external agents from the actuating unit.
During opening and closing of the dispensers outlet opening, the axial movement of the shutter subjects the membrane connected to it to constant bending and hence mechanical stress. Moreover, hot and/or aggressive liquid substances that flow through the dispensing conduit, for example when the dispenser s cleaned, subject the dispenser to further stress.
Usually, the membrane undergoes preventive maintenance because it has a limited theoretical working life, corresponding to a defined number of working cycles, normally indicated by the manufacturer. However, all the stresses the membrane is subjected to may cause it to break before the end of its theoretical working life, allowing the product to come into contact with external contaminating agents.
It is therefore important to detect a broken membrane promptly so that the quality of the product filled into the containers is maintained and guaranteed for the consumer.
One prior art solution for detecting when the flexible membrane breaks comprises providing a sealed chamber adjacent to the membrane inside the dispenser housing, with a connecting conduit which places the sealed chamber in communication with the external environment. A window made on the outside wall of the dispenser allows visual inspection of the connecting conduit. The presence of product in the conduit indicates that the membrane is broken because it has allowed product to flow into the sealed chamber adjacent to it and from there into the connecting conduit in communication with the inspection window.
The visual inspection is performed by an operator who, after detecting the presence of the product in the conduit, must stop the filling machine and carry out the appropriate maintenance.
The visual inspection may be carried out with a certain delay after the membrane has actually broken, making this detection system unreliable.
Moreover, added to the costs of machine maintenance are the costs of non-production due to machine down time needed to carry out the maintenance.
In other prior art solutions, there are sensors for automatically detecting broken membranes. The sensors are connected to a control system which communicates with the filling machine in such a way as to stop the filling machine immediately after detecting the broken membrane, thus allowing the operator to carry out the necessary maintenance.
The systems with automatic sensors are more reliable than those which depend on visual inspection but continue to entail machine down time for maintenance of the dispensing device, resulting in costs arising out of non-production.